The present invention relates to a Universal Serial Bus device and more particularly to a Universal Serial Bus device that includes a rechargeable unit that recharges through the Universal Serial Bus.
The Universal Serial Bus (USB) specification is a proposed standard recently promulgated by a group of computer companies including Compaq Computer Corporation, Digital Equipment Corporation, IBM, Intel Corporation, Microsoft Corporation and Northern Telecom. Described below are various aspects of the Universal Serial Bus. The Universal Serial Bus is intended as a bi-directional, isochronous, low-cost, dynamically attachable, serial interface to promote easy PC peripheral expansion and provide full support for real-time voice, audio, and compressed video data. The Universal Serial Bus provides two-wire point-to-point signaling in which the signals are differentially driven at a bit rate of 12 megabits per second. The Universal Serial Bus includes support for both isochronous and asynchronous messaging at the 12 megabit per second data speed.
The USB specification introduces a new type of bus structure to replace the existing serial peripheral bus. The USB standard specifies USB devices known as xe2x80x9chubsxe2x80x9d that provide attachment points for other USB devices, such as USB-compliant peripherals (called xe2x80x9cfunctionsxe2x80x9d). Hubs are of three basic types: bus-powered and self-powered. Bus-powered hubs draw all their power from their USB connection, while self-powered hubs draw power from an exteral power source, or a hybrid of both the external power source and the USB. Bus-powered and self-powered hubs both provide power to devices attached to them. However, a bus-powered hub can only redistribute the amount of power it receives from its connection to the USB, and each downstream port on a bus-powered hub can supply a maximum of 100 mA to its attached device. A self-powered hub should be able to supply up to 500 mA to each downstream device attached to the hub.
Functions are likewise divided into bus-powered and self-powered classes, with bus-powered functions further categorized as low-power and high-power. Low-power functions can be powered from either type of hub, but high-power functions should be connected to self-powered hubs in order to have sufficient power to operate. Low-power functions are generally peripherals such as a mouse or a keyboard; high-power functions include printers and speakers. Self-powered functions can be attached to either type of hub as the function does not draw its operating power from the hub, although it can draw minimal power from the USB to support itself when in a suspended state. USB hubs and functions generally enter a minimal power xe2x80x9csuspendxe2x80x9d state when they detect no I/O activity on their USB connections for a certain period of time. During normal operations, each hub is responsible for passing on a polling signal from the USB host to the devices attached to the hub to prevent the hubs from suspending. Suspended hubs typically cannot transfer data on the bus until enabled by a xe2x80x9cresumexe2x80x9d command.
In some situations, an individual using a computer may need to utilize a high powered peripheral device that draws current higher than that permitted by the USB specification, such as a zip drive or a wide area network radio, when the individual does not have access to an external power source. These type of peripherals generally have very high peak continuous current demands that when averaged over hours draw very little current. For example, if the individual is on an airplane he/she may desire to store work on the zip drive. Although the zip drive only will be used for a short period of time and has a low average current draw over time, it draws a great deal of power during powering up, which cannot be made available by a USB powered device due to the strict power constraints of the USB bus power rules. Therefore, it would be necessary to provide a device with a battery that can provide large amounts of current for a short period of time. Such a device would be impractical because the battery in the device would have to be either very large or it would discharge so rapidly that it would continually need to be replaced. If the battery were a rechargeable device it would have to be continuously recharged by an external recharging device. If an external recharging device was available, then it would not be necessary to utilize a battery to provide a self powered device in the first place.
Accordingly, there is a strong need in the art for a device that can provide the necessary short term power to the high powered peripherals as described above, and that can be reused, while still adhering to the strict power requirements of the USB specification.
According to a preferred embodiment of the present invention, a function device or USB remote hub is provided that includes a large energy well (e.g. rechargeable device such as a battery or large capacitor) for providing the required power to peripherals when the peripheral device requires more power than the USB allows. The large energy well or rechargeable device shall charge using current drawn from the USB bus and terminate charge by the controller or discrete circuitry provided on the function or remote hub. The rechargeable device shall draw current from the USB at a maximum of 100 ma during power up and then may enter a high power bus powered mode, so that it can draw the maximum 500 ma of current provided by the USB. The rechargeable device will turn off or draw a sleep current of less than 500 xcexca when the USB is placed in a suspend state. The device may optionally be configured to provide remote wake up functionality to provided support to the USB power management to allow recharging to resume.
Thus, according to one aspect of the present invention, a remote function device is provided coupleable to a host computer through a Universal Serial Bus port. The remote function device includes a function controller coupleable to the host computer, a mode and status system coupled to the function controller and a rechargeable device coupled to the mode and status system. The rechargeable device is adapted to drive a peripheral device wherein the rechargeable device draws current from the Universal Serial Bus to charge the rechargeable device to a predetermined charge level for driving the peripheral device, the predetermined charge level exceeding a charge level that can be provided directly from the Universal Serial Bus.
In accordance with another aspect of the present invention a remote hub device is provided that is coupleable to a host computer through a Universal Serial Bus port. The remote hub device includes a hub controller coupleable to the host computer, a mode and status circuit coupled to the hub controller, and rechargeable device coupled to the mode and status circuit. The rechargeable device is adapted to provide current to at least four power ports, each port having means for limiting the current through the port, wherein the rechargeable device draws current from the Universal Serial Bus to charge the rechargeable device to a predetermined charge level for providing the current to the at least four power ports.
In accordance with yet another aspect of the present invention, a method of charging a rechargeable device on a Universal Serial Bus device coupled to a host computer is provided. The method includes the steps of initializing the Universal Serial Bus device in a low charge rate, configuring the Universal Serial Bus device to operate in a high power bus powered mode, charging the rechargeable device at a high charge rate until the rechargeable device reaches a predetermined charge level for the high charge rate, and charging the device at a low charge rate until the rechargeable device reaches a predetermined charge level for the low charge rate.
In accordance with another aspect of the present invention, a remote Universal Serial Bus device is provided that is coupleable to a host computer through a Universal Serial Bus port. The device includes means for powering a high powered peripheral device, the means for powering the high powered peripheral device being rechargeable, means for monitoring the charge level of the means for powering the high powered peripheral device, means for changing the charge level of the means for powering the high powered peripheral device, and means for controlling the configuration of the Universal Serial Bus device, which communicates to the host computer wherein the means for controlling the configuration of the Universal Serial Bus device configures the Universal Serial Bus device as a high power bus powered device after power up.
In accordance with yet another aspect of the present invention a remote function device is provided that is coupleable to a host computer through a Universal Serial Bus port. The device includes a function controller coupleable to the host computer, a mode and status circuit coupled to the function controller, and a rechargeable device coupled to the mode and status circuit. The rechargeable device is adapted to drive a high powered peripheral device wherein the rechargeable device draws more than 100 ma and less than 500 ma from the Universal Serial Bus to charge the rechargeable device to a predetermined charge level for a high charge rate, then the rechargeable device draws less than 100 ma until the rechargeable device reaches a predetermined charge level for a low charge rate, wherein the rechargeable device stops charging at the low charge rate upon reaching the predetermined charge level for the low charge rate.